Single-belt conveyor

ABSTRACT

A belt conveyor having a conveyor belt which is flexible in the transverse direction and which, along part of its path of travel, is twisted about it own axis from a lower guide roller (2) to an upper guide roller (3) for forming a tube for the conveyance of goods. The belt (1) runs over the guide rollers in a transversely substantially straightened state. The guide rollers (2, 3), in dependence upon the pitch of the belt (1) in the twisted part thereof, are so inclined relative to the center line of the tube that the two edge portions (6, 7) of the belt in the twisted part thereof engage each other substantially edge to edge. The edge portions (6, 7) of the belt (1) have substantially inextensible reinforcements (8, 9) for taking up longitudinal tensile forces in the belt. The belt is further so stretched and twisted between the guide rollers (2, 3) that the edge portions (6, 7) in the twisted part of the belt engage each other substantially edge to edge and follow helical lines which are contained in a cylinder surface having a smaller diameter than the diameters of the cylinder surfaces in which the helical lines for other longitudinal portions of the belt are contained.

The present invention relates to a belt conveyor having a conveyor beltwhich is flexible in the transverse direction and which, along part ofits path of travel, is twisted about its own axis from a lower guideroller to an upper guide roller for forming a tube for conveying goods,the belt running over the guide rollers in a transversely substantiallystraightened state.

For the closed conveyance of bulk goods, belt conveyors having aconveyor belt formed into a tube are previously known in the art. Therim or edge portions of the conveyor belt are then held together bymutually engaging means on the very rim portions or by external means.One example of the latter technique is a tube which is formed from abelt of uniform cross-sectional shape by means of a plurality of sets ofrollers with a large number of rollers distributed around the peripheryof the tube. In this way, the tube will be closed by a considerableoverlap of the inner side of the belt on the outer side thereof, whetherthe belt is twisted about its own axis or not. In the case of a twistedbelt, it is known to make the overlap extend throughout the entirecircumference of the tube, such that the thickness of the tube wall willalways be twice the thickness of the belt.

The considerable overlap in the last-mentioned conveyors entails arelatively low transport capacity as compared with conveyors whose rimportions are held together by engagement means provided on the rimportions of the belt, i.e. for the same belt width and belt velocity.However, the manufacturing costs for belts having such engagement meansare comparatively high and there is a risk that the engagement meanswill be clogged by the goods conveyed so as to be unable to performtheir retaining function properly.

The object of the present invention therefore is to provide a beltconveyor of the type mentioned in the introduction to thisspecification, which has a simple construction and is relativelyinexpensive, and yet ensures a high transport capacity.

The contemplated belt conveyor should also be especially well suited fora more or less vertical conveyance of goods.

According to one aspect of the invention, this object is achieved by abelt conveyor which is characterized in that the guide rollers, independence upon the pitch of the belt in the twisted part thereof, areso inclined in relation to the centre line of the tube that the two edgeportions of the belt in the twisted part thereof engage each othersubstantially edge to edge.

The belt according to the invention may be extensible, e.g. byconsisting of an elastic material such as rubber, but the extensibilityof the edge portions of the belt is suitably less in the longitudinaldirection of the belt than the extensibility of the rest of the belt.The belt may however have the same elasticity in the longitudinaldirection throughout the entire cross-section and consist e.g. of rubberwith a uniform reinforcing fabric throughout the entire width and lengthof the belt.

In a first embodiment, the edge portions of the belt have substantiallyinextensible reinforcements for taking up longitudinal tensile forces inthe belt. The longitudinal portions of the belt adjacent its edgeportions will thus follow helical lines having a smaller diameter, i.e.the diameter of the cylinder surface in which the helical lines arecontained, than longitudinal belt portions located at a greater distancefrom the two edge portions of the belt.

In a second embodiment in which the belt has a constant extensibilitythroughout the cross-section, the entire belt is however contained insubstantially the same cylinder surface, possibly with the exception ofthe outer edge portions which then project outside this cylindersurface.

By the orientation of the guide rollers according to the invention, thebelt will have no or only a slight tendency to move axially on the guiderollers and, without the use of any particular sets of guide rollers forforming and maintaining the tube, it will pass over the rollers in thetransversely substantially straightened state in such a manner that theedges of the belt, at that part of the belt which makes contact with aguide roller, will be contained in radial planes to the axis of theguide roller. In order to further ensure that the belt will not movesideways on the guide rollers, these may be cambered.

According to the invention, the inclination or orientation of the guiderollers thus is determined by the pitch of the belt in the twisted partthereof or, in other words, by the number of full turns and parts of aturn the belt is twisted about its own axis between the guide rollers.In its path of return, the belt may travel either in a planar state orin a twisted state, suitably twisted in a direction opposite to that inwhich it is twisted when travelling from the lower guide roller to theupper guide roller, or in a combination of said two states.

The inlet opening and the outlet opening of the conveyor tube can bearranged, as desired, on any side of the belt, i.e. the point of infeedcan be located on the side of the belt which faces/faces away from theguide roller at the point of infeed. Similarly, the point of outfeed canbe located on the side of the belt which faces/faces away from the guideroller at the point of outfeed.

When the point of infeed of the goods at the lower guide roller isdisposed on the side where the belt leaves the guide roller, the beltrun travelling upwards from the lower guide roller may be so immersed inthe goods to be transported that the lower opening of the tube issituated entirely underneath the surface of the goods. This can beachieved by arranging an infeed container at the lower guide roller,this container enclosing the belt run travelling upwards from the lowerguide roller, and having a slot at its bottom for admitting the belt runinto the container.

By the present invention, the belt is formed into a closed tube in avery short distance. This distance can be further reduced by means of apressure roller provided at each guide roller. The pressure roller isthen placed so as to press against that of the two edge portions of thebelt which has the lowest tension. The fact that the belt has differenttension in its edge portions adjacent each guide roller is because theedge portions describe different paths of movement up to the point wherethey enter into contact with each other. By using such pressure rollers,variations otherwise existing in the tension along the edge portionsbetween the guide rollers are equalized, such that the relative slidingmovement or friction between the edge portions in the twisted part ofthe belt is minimized.

According to another aspect of the invention, the object indicated aboveis achieved in that the edge portions of the belt have substantiallyinextensible reinforcements for taking up longitudinal tensile forces inthe belt and in that the belt is so stretched and twisted between theguide rollers that the edge portions in the twisted part of the beltengage each other substantially edge to edge and follow helical lineswhich are contained in a cylinder surface having a smaller diameter thanthe diameters of the cylinder surfaces in which the helical lines forother longitudinal portions of the belt are contained.

The invention will be described in greater detail hereinbelow withreference to the accompanying drawings.

FIG. 1 is a side view of a first embodiment of the belt conveyoraccording to the invention and illustrates the principle design thereof.

FIGS. 2, 3 and 4 are cross-sections of the belt taken along the linesII--II, III--III and IV--IV, respectively, in FIG. 1.

FIG. 5 is a side view of a second embodiment of a belt conveyoraccording to the invention.

FIGS. 6 and 7 illustrate different possible orientations of guiderollers for the belt, the actual orientation being not shown in theother Figures.

FIGS. 8 and 9 show different positions of the point of infeed of thegoods.

FIGS. 10 and 11 show different positions of the point of outfeed of thegoods.

FIG. 12 is cross-section of a belt tube.

FIG. 13 shows a feeder device.

The belt conveyor illustrated in FIG. 1 has a conveyor belt 1 which isguided over end rollers 2 and 3 from a point for infeed of goods,indicated by an arrow 4, to a point for outfeed of goods indicated by anarrow 5. The conveyor belt 1 travels in a closed path from the point ofinfeed 4 to the point of outfeed 5, over the upper guide roller 3, andreturns via the lower guide roller 2 to the point of infeed 4. The belt1 is flexible in the transverse direction by being made of an elasticmaterial, such as rubber. From the point of infeed 4 to the point ofoutfeed 5, the belt 1 is twisted about its own axis, such that the twoedge portions 6, 7 of the belt 1 engage each other and form a tube forconveying the goods throughout the major part of the distance betweenthe point of infeed 4 and the point of outfeed 5.

At the point of infeed 4, the conveyor tube formed by the belt 1 has afeed or inlet opening which is defined between the point where the belt1 leaves the guide roller 2 and where the edge portions 6 and 7 of thebelt are maximally spaced from each other, and the point where the edgeportions 6 and 7 enter into engagement with each other. The transitionof the belt from the planar to the closed state is illustrated in FIGS.2, 3 and 4. Although the belt 1 may be homogeneous and consist of thesame material throughout its entire width, it may be convenient in somecases to make its edge portions less extensible in the longitudinaldirection of the belt than the rest of the belt. The edge portions ofthe belt 1 may for instance have substantially inextensiblereinforcements for taking up longitudinal tensile forces in the belt.These reinforcements may consist of fabric inserts, such as cords, orsteel wires 8, 9. However, the reinforcements may also be external andmay for instance project from the profile of the rest of the belt, whilebeing connected to the belt. In the case where the edge portions 6 and 7of the belt 1 are less extensible in the longitudinal direction than therest of the belt, the helical lines which the edge portions 6, 7 follow,will be contained in a cylinder surface 10 having a smaller diameterthan the diameters of the cylinder surfaces in which the helical linesfor other longitudinal portions of the belt 1 are contained. The belt 1,with its periphery, will enclose a straight line, indicated by a dot 11in FIG. 4, between the point of infeed 4 and the point of outfeed 5.

In the embodiment according to FIG. 1, the belt 1 is also twisted in itspath of return from the guide roller 3 to the guide roller 2, preferablyto an equal extent as and in a direction opposite to that in which thebelt 1 is twisted when travelling from the point of infeed 4 to thepoint of outfeed 5. In the free state, it is thus possible to define aninner side and an outer side of the belt, i.e. the belt is not twistedat all.

An alternative embodiment is illustrated in FIG. 5 where the distance ofconveyance of the goods is equal to that in the embodiment of FIG. 1.Instead of directly returning the belt from the guide roller 3 to theguide roller 2, the embodiment according to FIG. 5 comprises anotherfour rollers 12, 15 defining the path of return of the belt 1 from theguide roller 3 to the guide roller 2. In this embodiment, the belt 1 isnot twisted in its path of return but travels in a transverselystraightened state along said path. The guide rollers 13 and 14 may bepositionally adjustable in order to give the belt 1 a suitable tension.The belt 1 is suitably driven by the roller 3 or the rollers 13 and 14.

Since the belt 1 is twisted about its own axis between the rollers 2 and3, the longitudinal direction of the belt, immediately adjacent theserollers, will not be parallel to a line interconnecting mutuallycorresponding points on these rollers. In order that the belt 1 shouldnot tend to move off the rollers, the guide rollers should be sooriented that the edges of the belt, at that part of the belt whichmakes contact with a guide roller, are in radial planes with respect tothe axis of the guide roller. If the belt 1 is twisted an uneven numberof half turns about its own axis, such an inclination of the guiderollers 2 and 3 relative to the centre line of the tube is required asis schematically illustrated in FIG. 6, it being presupposed that theaxes of the guide rollers 2 and 3 are in one and the same plane. In thismanner, the two edge portions 6, 7 of the belt 1 in the twisted partthereof will engage each other substantially edge to edge. Thus, thereis substantially no overlapping of the belt. If the belt 1 is twisted aneven number of half turns about its own axis, i.e. a number of fullturns, such an orientation of the guide rollers 2 and 3 as shown in FIG.7 is required.

Different in- and outfeed devices are conceivable in combination withthe belt conveyor according to the invention. It is however desirablethat the goods supplied be imparted a component of motion in thedirection of travel of the belt 1 from the point of infeed 4 to thepoint of outfeed 5. As shown in FIG. 8, the point of infeed may belocated on that side of the belt which is facing away from the guideroller 2 but may also, as shown in FIG. 9, be located on the side of thebelt facing the guide roller 2. Similarly, the outfeed device should beassociated with the outlet opening of the tube, which may be located onthe side of the belt facing away from the guide roller 3, as shown inFIG. 10, or on the side of the belt facing the guide roller 3, as shownin FIG. 11.

Both the distance of infeed and the distance of outfeed aresubstantially determined by the belt width and may, if the belt is fullystraightened in the transverse direction, have a length of approximatelyfour times the belt width. These distances can be reduced to some extentby means of suitably positioned pressure rollers 21 which, at any rate,may ensure effective closure of the tube at the beginning and at the endof the distance of conveyance, while equalizing the tension in the edgeportions of the belt. For example, a pressure roller 21 may be providedbetween the guide roller 2 and the point where the edge portions 6, 7 ofthe belt engage each other.

As an example of a usable pitch, the length of one torsional turn of thebelt may amount to approximately six times the belt width. Beltvelocities in the order of 5-10 m/sec. are possible, which means a veryhigh transport capacity.

Since the belt is twisted, the goods will rotate about the centre of theconveyor tube when being transported from the point of infeed to thepoint of outfeed and, thus, be subjected to a centrifugal force. In theembodiment according to FIG. 4 using edge reinforcements, thecentrifugal force will be greatest at a maximum distance from the edgeportions, for which reason the goods tend to move away from the edgeportions. As a result, the conveyor may even be used for transportingliquids without necessitating a liquid-proof contact between the edgesof the belt.

The belt may pass over a guide roller in twisted or untwisted tubularshape. The radius of curvature of the tube over the guide roller mustthen be large in relation to the tube diameter. When the tube passesover a guide roller in the untwisted state, it is advantageous if thebelt has distinct tractive edges which are together guided in towardsthe roller, for instance, in a wedge-shaped groove, the tube beinglocated radially outwardly of the groove.

Many modifications of the embodiments described above are possiblewithin the inventive scope. Thus, in order to relieve the belt, it ispossible to provide separate wires. In addition, these may be applied soas to tend to urge the edge portions of the belt against each other tofurther seal the tube.

One or more wires can also be caused to run inside the conveyor tubebetween the point of infeed and the point of outfeed and then serve toentrain the goods and, to that end, may optionally be provided withwidened portions at suitable intervals. These widened portions may havea cross-sectional shape corresponding to the cross-sectional shape ofthe conveyor tube and are then directly load-carrying.

FIG. 12 is a cross-sectional view of a tube which is formed from a beltof uniform cross-section and substantially constant extensibilitythroughout the cross-section. In this case, the edge portions 6, 7 willengage each other substantially edge to edge in a slightly projectingstate with respect to the cylinder surface in which the rest of the belt1 is contained. Thus, substantially no such overlap exists as in thetubes of the conventional technique but the inner side of the belt atone edge portion may approach and even engage the inner side of the beltat the other edge portion.

FIG. 13 shows a container 16 which is arranged at a lower guide roller2' and provided at its bottom with a slot 17 through which the run ofthe belt 1 travelling upwards from the guide roller 2' enters into thecontainer 16. This has a sufficient height to enable the goods fed intothe container to completely cover the lower funnel-shaped opening of thetube, such that the belt 1 will entrain the goods into the tube forhoisting it to an upper guide roller.

It should finally be emphasized that the belt conveyor according to theinvention is suitable for conveying any type of goods, including piecegoods, bulk goods, liquids and goods suspended in liquids.

We claim:
 1. A belt conveyor having a conveyor belt which is flexible inthe transverse direction and which, along part of its path of travel, ishelically twisted about its own axis from a lower guide roller (2) to anupper guide roller (3) for forming a tube for conveying goods, the belt(1) running over the guide rollers in a transversely substantiallystraightened state, wherein the upper and lower guide rollers (2, 3) areso oriented relative to the center line of the tube that the two edgeportions (6, 7) of the belt in the twisted part thereof aresubstantially non-overlapping and engage each other substantially edgeto edge.
 2. Belt conveyor as claimed in claim 1, wherein the belt (1) isextensible but that its edge portions (6, 7) are less extensible in thelongitudinal direction of the belt than the remainder of the belt. 3.Belt conveyor as claimed in claim 1 wherein, the edge portions (6, 7) ofthe belt (1) have substantially inextensible reinforcements (8, 9) fortaking up longitudinal tensile forces in the belt.
 4. Belt conveyor asclaimed in claim 1, wherein the belt (1) is also twisted in its path ofreturn from the upper guide roller (3) to the lower guide roller (2) inthe opposite direction with respect to how it is twisted when travellingfrom the lower guide roller to the upper guide roller.
 5. Belt conveyoras claimed in claim 1, wherein a goods infeed point is arranged that thelower guide roller (2) on the side where the belt leaves said lowerguide roller.
 6. Belt conveyor as claimed in claim 1, wherein the beltrun travelling upwards from the lower guide roller (2) is so immersed inthe goods to be conveyed that the lower opening of the tube is locatedcompletely underneath the surface of the goods.
 7. Belt conveyor asclaimed in claim 6, further comprising a container (16) for the infeedof goods at the lower guide roller (2'), which container encloses thebelt run travelling upwards from the lower guide roller and having aslot (17) for the introduction of said belt run at the bottom of thecontainer.
 8. Belt conveyor as claimed in claim 1, further comprising apressure roller provided at each guide roller (2, 3), said pressureroller being pressed against one of the edge portions (6, 7) of the beltbetween the guide roller and the point where the edge portions (6, 7) ofthe belt engage each other.
 9. Belt conveyor having a conveyor beltwhich is flexible in the transverse direction and which, along parts ofits path of travel, is helically twisted about its own axis from a lowerguide roller (2) to an upper guide roller (3) for forming a tube forconveying goods, the belt (1) running over the guide rollers in atransversely substantially straightened state, wherein the edge portions(6, 7) of the belt (1) have substantially inextensible reinforcements(8, 9) for taking up longitudinal tensile forces in the belt, and thatthe belt is so stretched and twisted between the upper and lower guiderollers and the upper and lower guides rollers are so oriented withrespect to the center line of the belt (2, 3) that the edge portions (6,7) in the twisted part of the belt are substantially non-overlapping andengage each other substantially edge to edge and follow helical linescontained in a cylinder surface of a smaller diameter than the diametersof the cylinder surfaces in which the helical lines for otherlongitudinal portions of the belt are contained.
 10. Belt conveyor asclaimed in claim 9, wherein the belt (1) is also twisted in its path ofreturn from the upper guide roller (3) to the lower guide roller (2) inthe opposite direction with respect to how it is twisted when travellingfrom the lower guide roller to the upper guide roller.